Pre-moistened wipes or hygiene tissue, are commonly used for cleansing different parts of the human body. Examples of specific uses are for baby care, hand wiping, feminine care and as toilet paper or a complement to toilet paper.
Since a long period of time often elapses from the time of manufacture of pre-moistened wipes until the time of use, they must have a sufficient structural integrity for their intended wiping function during such period. Adding a wet strength agent to the wipe will provide such wet integrity. However, especially when used as toilet paper, there is a strong desire that the wipe or tissue can be flushed in the sewer without causing problems with blocked pipes and filters. Wipes or tissue having a high wet strength will not disintegrate or break up into small fibre clumps when flushed in conventional household toilet systems, which may cause plugging of the drainage system.
It is previously known, for example through U.S. Pat. No. 3,554,788 to use an adhesive having a water-soluble component as a bonding agent in a water dispersible nonwoven material. The material is alleged to have a good dry strength but readily disperses in water and is flushable. This nonwoven material is packaged in dry condition and would not retain sufficient structural integrity for any longer period of time as is required for wet wipes.
A wet wipe made of a hydroentangled three ply sandwich structure including outer layers of synthetic fibers and a middle layer of cellulosic fibers is known through U.S. Pat. No. 6,110,848.
Most moist flushable pre-moistened toilet papers which are on the market today are flushable due to their small size. They can move along the drainage and sewage pipes, but are not readily dispersible and may therefore cause problems with blocked pipes and filters.
US 2004/0112783 discloses dry tissue paper and a storage box therefore, wherein the tissue paper is prevented from being torn when removed from the box by having specified tensile strength in longitudinal and lateral direction. In a dry condition the longitudinal tensile strength is 2.5 to 3.5 times higher than the lateral tensile strength.
JP-A-2006181764 discloses a water-degradable wipe formed using a hydration paper having a multi-ply structure. The water-degradable wipe is impregnated with an aqueous washing agent containing metal ion of alkaline metal ion. It has a ratio of wet strength in machine direction and cross machine direction of 1.0 to 3.5 and a wet strength in cross machine direction of less than 0.5 N/25 mm.